The phosphorylation of proteins and lipids is an important cellular regulation mechanism which plays a role in many different biological processes such as cell proliferation, differentiation, apoptosis, metabolism, inflammation, immune reactions and angiogenesis. More than 500 kinases are encoded in the human genome. In general, tyrosine protein kinases are stimulated by growth factors or other mitogenic signals and phosphorylate proteins which initiate rapid signal transmissions. Serine/threonine protein kinases mostly phosphorylate proteins which crosslink and amplify intracellular signals. Lipid kinases are likewise important switching sites in intracellular signal pathways, with these sites linking various biological processes.
A number of protein kinases have already proved to be suitable target molecules for therapeutic intervention in a variety of indications, e.g. cancer and inflammatory and autoimmune diseases. Since a high percentage of the genes involved in the development of cancer which have been identified thus far encode kinases, these enzymes are attractive target molecules for the therapy of cancer in particular.